Polycarbonate resin compositions

ABSTRACT

Polycarbonate resin compositions and methods for their preparation are disclosed. The disclosed compositions are comprised of polycarbonate resins and esters of aliphatic carboxylic acids and alcohols and exhibit good mold release and thermal stability while experiencing little discoloration during molding.

The present invention relates to polycarbonate resin conditions,specifically to polycarbonate resin compositions having good moldrelease and thermal stability.

BACKGROUND OF THE INVENTION

Polycarbonates are usually manufactured by the phosgene process, butpolycarbonates obtained in this way have the drawbacks of unsatisfactorythermal stability, and of poor mold release which complicates thecontinuous production of molded products from such polycarbonates.

In order to improve the mold release characteristics of polycarbonates,aliphatic ester are sometimes mixed with them as mold release agents.But although the addition of aliphatic esters makes for better moldrelease, the resin compositions thus obtained have inferior thermalstability, which can cause problems such as mold fouling duringcontinuous production of molded products.

Those problems are solved by the present invention, whose object is toprovide polycarbonate resin compositions having good mold release andthermal stability, with minimal mold fouling.

SUMMARY OF THE INVENTION

The present invention consists of polycarbonate resin compositionscontaining

A) 100 wt. parts polycarbonates and

B) 0.001˜5 wt. parts esters of aliphatic carboxylic acids and alcohols,

in which the polycarbonates are products of melt polymerization ofaromatic dihydroxy compounds with carbonate diesters.

These polycarbonate resin compositions have extremely good mold release.They also show very little discoloration during molding. In addition,they have good thermal stability, so there is little fouling of molds incontinuous production, and little lowering of melt viscosity duringmolding. These effects of the present invention are a dramaticimprovement over those observed when polycarbonates made by theconventional phosgene process are used, or when common mold releaseagents are added. It is this combination of polycarbonates and moldrelease agents in accordance with the present invention that makespossible the effect of the invention.

These polycarbonate resin compositions are particularly suitable for usein optical applications, such as optical disks, lenses, optical fibers,lighting fixtures, etc.

The first essential condition of the present invention is the use ofpolycarbonates which are products of melt polymerization of aromaticdihydroxy compounds with carbonate diesters. As shown by the comparisonsbelow, such an effect cannot be achieved when ordinary polycarbonatesobtained by the phosgene process are used, even with added esters. Onthe other hand, using polycarbonates which are products of meltpolymerization of aromatic dihydroxy compounds with carbonate diesters,in accordance with the present invention, the characteristics discussedabove can be dramatically improved by addition of the esters. This issomething completely unforeseen.

The products of melt polymerization of aromatic dihydroxy compounds withcarbonate diesters referred to here include all polycarbonates obtainedby a melt process using aromatic dihydroxy compounds and carbonatediesters as the starting materials. The melt process itself is a knownmethod of synthesizing polycarbonates by a transesterification reactionbetween dihydroxy compounds and carbonate diesters in their moltenstate.

There is no particular restriction on the aromatic dihydroxy compounds;any of the various types of known compounds can be used. Examplesinclude, but are not limited to, compounds represented by the formula##STR1## (where R^(a) and R^(b) are each independently a halogen or amonovalent hydrocarbyl group; X is --C(R^(c))(R^(d))--, --C(═R^(e))--,--O--, --S--, or --SO₂ --, R^(c) R^(d) are each independently a hydrogenatom or a monovalent hydrocarbyl group; R^(f) is a divalent hydrocarbylgroup; and p and q are each independently an integer 0˜4), such asbis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxy-tert-butylphenyl)propane,2,2-bis(4-hydroxy-3-bromophenyl)propane, and other bis(hydroxyaryl)alkanes; 1,1-bis(4-hydroxyphenyl)cyclophentane,1,1-bis(4-hydroxyphenyl)cyclohexane, and otherbis(hydroxyaryl)cycloalkanes; 4,4'-dihydroxydiphenyl ether,4,4'-dihydroxy-3,3'-dimethylphenyl ether, and other dihydroxyarylethers; 4,4'-dihydroxydiphenyl sulfide,4,4'-dihydroxy-3,3'-dimethylphenyl sulfide, and other dihydroxyarylsulfides; 4,4'-dihydroxydiphenyl sulfoxide,4,4'-dihydroxy-3,3'-dimethylphenyl sulfoxide, and other dihydroxyarylsulfoxides; and 4,4'-dihydroxydiphenyl sulfone,4,4'-dihydroxy-3,3'-dimethylphenyl sulfone, and other dihydroxyarylsulfones. Of these, 2,2-bis(4-hydroxyphenyl)propane is preferably used.Other aromatic dihydroxy compounds which can be used include compoundsrepresented by the following general formula ##STR2## (where each R' isindependently a hydrocarbyl group having 1-10 carbons, a halogenatedhydrocarbyl group having 1-10 carbons, or a halogen atom, and m is aninteger 0˜4), such as resorcin, 3-methylresorcin, 3-ethylresorcin,3-propylresorcin, 3-butylresorcin, 3-tert-butylresorcin,3-phenylresorcin, 3-cumylresorcin, 2,3,4,6-tetrafluororesorcin,2,3,4,6-tetrabromoresorcin, and other substituted resorcins; catechol;hydroquinone, 3-methylhydroquinone, 3-ethylhydroquinone,3-propylhydroquinone, 3-butylhydroquinone, 3-tert-butylhydroquinone,3-phenylhydroquinone, 3-cumyulhydroquinone,2,3,5,6-tetramethylhydroquinone, 2,3,5,6-tetra-tert-butylhydroquinone,2,3,5,6-tetrafluorohydroquinone, 2,3,5,6-tetrabromohydroquinone, andother substituted hydroquinones; as well as2,2,2',2'-tetrahydro-3,3,3',3'-tetramethyl-1,1'-spirobi-[1H-indenel]-7,7'-diolrepresented by the following formula. ##STR3##

These aromatic dihydroxy compounds may be used singly or in combinationsof two or more.

There is no particular restriction on the carbonate diesters, either.Examples include, but are not limited to, diphenyl carbonate, ditolylcarbonate, bis-(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthylcarbonate, bis(diphenyl) carbonate, diethyl carbonate, dimethylcarbonate, dibutyl carbonate, dicyclohexyl carbonate, etc. Diphenylcarbonate is preferably used.

These carbonate esters may be used singly or in combinations of two ormore.

These carbonate diesters may also contain dicarboxylic acids ordicarbonxylate esters. Examples of dicarboxylic acids and dicarboxylateesters include aromatic dicarboxylic acids and their derivatives, suchas terephthalic acid, isophthalic acid, diphenyl terephthalate, diphenyliosphthaliate, etc.; aliphatic dicarboxylic acids and their derivatives,such as succinic acid, glutaric acid, adipic acid, pimelic acid, subericacid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid,diphenyl sebacate, diphenyl decanedioate, diphenyl dodecanedioate, etc.;and alicyclic dicarboxylic acids and their derivatives, such ascyclopropanedicarboxylic acid, 1,2-cyclobutanedicarboxylic acid,1,3-cyclobutanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid,1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,diphenyl cyclopropanedicarboxylate, diphenyl1,2-cyclobutanedicarboxylate, diphenyl 1,3-cyclobutanedicarboxylate,diphenyl 1,2-cyclopentanedicarboxylate, diphenyl1,3-cyclopentanedicarboxylate, diphenyl 1,2-cyclopentanedicarboxylate,diphenyl 1,4-cyclohexanedicarboxylate, etc. These dicarboxylic acids anddicarboxylate esters may be used singly or in combinations of two ormore. The carbonate diesters preferably contain no more than 50 mole %,more preferably no more than 30 mole %, of such dicarboxylic acids anddicarboxylate esters.

In the manufacture of the polycarbonates, in addition to the aromaticdihydroxy compounds and carbonate diesters, one can also usepolyfunctional compounds having three or more functional groups permolecule. Such polyfunctional compounds are preferably compounds havingphenolic hydroxy groups or carboxy groups; those having 3 phenolichydroxy groups are particularly preferred. Examples of such preferredcompounds include 1,1,1-tris(4-hydroxyphenyl)ethane,2,2',2"-tris(4-hydroxyphenyl)diisopropylbenzene [sic],α-methyl-α,α',α'-tris(4-hydroxyphenyl)-1,4-diethylbenzene,α,α',α"-tris-(4-hydroxyphenyl)-1,3,5-trisopropylbenzene, phloroglucin,4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptane-2,1,3,5-tri(4-hydroxyphenyl)benzene,2,2-bis[4,4-(4,4'-dihydroxyphenyl)cyclohexyl]propane, trimellitic acid,1,3,5-benzenetricarboxylic acid, pyromellitic acid, etc. Particularlypreferred are 1,1,1-tris(4-hydroxyphenyl)ethane,α,α',α"-tris(4-hydroxyphenyl)-1,3,5-tri-isopropylbenzene, etc. Thepolyfunctional compounds are preferably used in amounts of up to 0.03mole, more preferably 0.001˜0.02 mole, most preferably 0.001˜0.01 mole,per mole of aromatic dihydroxy compounds.

Compounds which form one or more terminal groups represented by theformula ##STR4## (where the aromatic ring or the chromanyl group may besubstituted with halogens or alkyl groups having 1-9 carbons) can alsobe used in the manufacture of polycarbonates. Compounds capable ofintroducing hydroxyl groups (1) include diols such as bisphenol A.Compounds capable of introducing phenoxy groups (2) include phenol,diphenyl carbonate, etc. Compounds capable of introducingp-tert-butylphenoxy groups (3)include p-tert-butylphenol,p-tert-butylphenyl phenyl carbonate, p-tert-butylphenyl carbonate, etc.Compounds capable of introducing p-cumylphenoxy groups(p-phenylisopropylphenoxy groups) (4) include p-cumyl-phenol,p-cumylphenyl, phenyl carbonate, p-cumylphenyl carbonate, etc.Chromanylpenoxy groups (5) of the type indicated in the formula includethose having the following formulas. ##STR5##

Compounds capable of introducing groups represented by (5-1) include2,2,4-trimethyl-4-(4-hydroxyphenyl)chroman,2,2,4,6-tetramethyl-4-(3,5-dimethyl-4-hydroxyphenyl)chroman,2,3,4-trimethyl-2-ethyl-4-(3-nonyl-4-hydroxyphenyl-7-nonylchroman,2,2,4-trimethyl-4-(3,5-diethyl-4-hydroxyphenyl)-6-ethylchroman,2,2,4,6,8-pentamethyl-4-(3,5-dimethyl-4-hydroxyphenyl)chroman,2,2,4-triethyl-3-methyl-4-(4-hydroxyphenyl)chroman,2,2,4-trimethyl-4-(3-bromo-4-hydroxyphenyl)-6-bromochroman,2,2,4-trimethyl-4-(3,5-dibromo-4-hydroxyphenyl)-6-bromochroman,2,2,4-trimethyl-4-(3,5-dibromo-4-hydroxyphenyl)-6,8-dibromochroman, etc.Of these, 2,2,4-trimethyl-4-(4-hydroxyphenyl)chroman is particularlypreferred. Compounds capable of introducing groups represented by (5-2)include 2,2,3-trimethyl-3-(4-hydroxyphenyl)chroman,2,2,3,6-tetramethyl-3-(3,5-dimethyl-4-hydroxyphenyl)chroman,2,3,4-trimethyl-2-ethyl-3-(3-nonyl-4-hydroxyphenyl)-7-nonylchroman,2,2,3-trimethyl-3-(3,5-diethyl-4-hydroxyphenyl)-6-ethylchroman,2,2,3-6,8-pentamethyl-3-(3,5-dimethyl-4-hydroxyphenyl)chroman,2,2,3-triethyl-3-methyl-3-(4-hydroxyphenyl)chroman,2,2,3-trimethyl-3-(3-bromo-4-hydroxyphenyl)-6-bromochroman,2,2,3-trimethyl-3-(3,5-dibromo-4-hydroxyphenyl)-6-bromochroman,2,2,3-trimethyl-3-(3,5-dibromo-4-hydroxyphenyl)-6,8-dibromochroman, etc.Of these, 2,2,3-trimethyl-3-(4-hydroyphenyl)chroman is particularlypreferred. Compounds capable of introducing groups represented by (5-3)include 2,4,4-trimethyl-2-(2-hydroxyphenyl)chroman,2,4,4,6-tetramethyl-2-(3,5-dimethyl-2-hydroxyphenyl)chroman,2,3,4-trimethyl-4-ethyl-2-(3,5-dimethyl-2-hydroxyphenyl)-7-nonylchroman,2,4,4-trimethyl-2-(3,5-dimethyl-2-hydroxyphenyl)-6-ethylchroman,2,4,4,6,8-pentamethyl-2-(3,5-dimethyl-2-hydroxyphenyl)-6-ethylchroman,2,4,4-trimethyl-2-(3-bromo-2-hydroxyphenyl)chroman,2,4,4-trimethyl-2-(3-bromo-2-hydroxyphenyl)-6-bromochroman,2,4,4-trimethyl-2-(3,5-dibromo-2-hydroxyphenyl)-6-bromochroman,2,4,4-trimethyl-2-(3,5-dibromo-2-hydroxyphenyl)-6,8-dibromochroman, etc.Of these, 2,2,4-trimethyl-2-(2-hydroxyphenyl)chroman [sic] isparticularly preferred. Compounds capable of introducing groupsrepresented by (5-4) include 2,4,4-trimethyl-2-(4-hydroxyphenyl)chroman,2,4,4,6 -tetramethyl-2-(3,5-dimethyl-4-hydroyphenyl)chroman,2,4,4-triethyl-2-(4-hydroxyphenyl)chroman,2,3,4-trimethyl-4-ethyl-2-(3,5-dimethyl-4-hydroxyphenyl)-7-nonylchroman,2,4,4-trimethyl-2-(3,5-diethyl-4-hydroxyphenyl)-6-ethylchroman,2,4,4,6,8-pentamethyl-2-(3,5-dimethyl-4-hydroxyphenyl)-6-ethylchroman,2,4,4-trimethyl-2(3-bromo-4-hydroxyphenyl)chroman,2,4,4-trimethyl-2-(3-bromo-4-hydroxylphenyl)-6-bromochroman,2,4,4-trimethyl-2-(3,5-dibromo-4-hydroxyphenyl)-6-bromochroman,2,4,4-trimethyl-2-(3,5-dibromo-22-hydroxyphenyl)-6,8-dibromochroman,etc. Of these 2,4,4-trimethyl-2-(4-hydroxyphenyl)chroman is particularlypreferred. All of these compounds may also have halogen or C₁₋₉ alkylsubstituent groups on the aromatic or the aliphatic rings. Thesecompounds may be used singly or in combination of 2 or more. In thepresent invention, the residues of these dihydroxy compounds arepreferably no more than 50%, most preferably no more than 30%, of thetotal terminal groups.

The amount of carbonate diesters used should be 1.00˜1.30 moles, mostpreferably 1.01˜1.20 moles, per mole of aromatic dihydroxy compounds.The monomers should be made to react in the presence of a catalyst.

The catalyst used may be, for example, one of the compounds proposed bythe present applicants in the specification of Japanese PatentApplication No. 2-85218. Preferred examples include (a) organic acidsalts, inorganic acid salts, oxides, hydroxides, hydrides, oralcoholates of metals such as alkali metals or alkaline-earth metals.Specific examples of such compounds include, but are not limited to,sodium hydroxide, potassium hydroxide, lithium hydroxide, sodiumhydrogen carbonate, potassium hydrogen carbonate, lithium hydrogencarbonate, sodium carbonate, potassium carbonate, lithium carbonate,sodium acetate, potassium acetate, lithium acetate, sodium stearate,potassium stearate, lithium stearate, sodium boron hydroxide, lithiumboron hydroxide, sodium phenyl borate, sodium benzoate, potassiumbenzoate, lithium benzoate, disodium hydrogen phosphate, dipotassiumhydrogen phosphate, dilithium hydrogen phosphate, the disodium ordipotassium or dilithium salt of bisphenol A, the sodium or potassium orlithium salt of phenol, etc.; calcium hydroxide, barium hydroxide,magnesium hydroxide, strontium hydroxide, calcium hydrogen carbonate,barium hydrogen carbonate, magnesium hydrogen carbonate, strontiumhydrogen carbonate, calcium carbonate, barium carbonate, magnesiumcarbonate, strontium carbonate, calcium acetate, barium acetate,magnesium acetate, strontium acetate, calcium stearate, barium stearate,magnesium stearate, strontium stearate, etc. These compounds may be usedsingly or in combinations of two or more. The amount of such alkalimetal compounds and/or alkaline-earth metal compounds used is preferably10⁻⁸ ˜10⁻³ mole, more preferably 10⁻⁷ ˜10⁻⁶ mole, most preferably 10⁻⁷˜8×10⁻⁷ mole, per mole of aromatic dihydroxy compounds.

In addition to these alkali metal compounds and/or alkaline-earth metalcompounds, basic compounds (b) may also be used as catalysts. Examplesof basic compounds include, but are not limited to, nitrogen compoundssuch as substituted ammonium hydroxides having alkyl, aryl, or alkarylgroups, e.g., tetramethylammonium hydroxide, tetramethylammoniumhydroxide, tetrabutylammonium hydroxide, trimethylbenzylammoniumhydroxide, etc.; tertiary amines such as trimethylamine, triethylamine,dimethylbenzylamine, triphenylamine, etc.; secondary or primary amineshaving methyl, ethyl, or other alkyl groups or phenyl, tolyl, or otheraryl groups; ammonia; and basic salts such as tetramethylammoniumborohydride, tetrabutylammonium borohydride, tetrabutylammoniumtetraphenylborate, tetramethylammonium tetraphenylborate, etc. Of these,the ammonium hydroxides are particularly preferred. These basiccompounds may be used singly or in combinations of two or more.

In the present invention, by using as the catalyst a combination of theabove-mentioned

(a) alkali metal compounds and/or alkaline-earth metal compounds, and

(b) nitrogen-containing basic compounds,

it is possible to obtain high-molecular-weight polycarbonates with highpolymerization activity.

It is also possible to use as the catalyst a combination of

(a) alkali metal compounds and/or alkaline-earth metal compounds,

(b) nitrogen-containing basic compounds, and

(c) boric acid and/or borate esters,

When this type of combination is used as the catalyst, the (a) alkalimetal compounds and/or alkaline-earth metal compounds are preferablyused in the amounts specified above, and the (b) nitrogen-containingbasic compounds are preferably used in amounts of 10⁻⁶ ˜10⁻¹ mole, mostpreferably 10⁻⁶ ˜10⁻² mole, per mole of aromatic dihydroxy compounds.The (c) boric acid or borate esters are preferably compounds representedby the following general formula

    B(OR.sup.g).sub.r (OH).sub.3-r

(where R⁹ is a hydrogen atom, an aliphatic hydrocarbyl group, analicyclic hydrocarbyl group, or an aromatic hydrocarbyl group, and r isan integer 1˜3). Examples include boric acid, trimethyl borate, triethylborate, tributyl borate, trihexyl borate, triheptyl borate, triphenylborate, tritolyl borate, trinaphthyl borate, etc. Of these, triphenylborate is particularly preferred. The amount of (c) boric acid or borateester used as a catalyst along with the above-mentioned compounds (a)and (b) is preferably 10⁻⁶ ˜10⁻¹ mole, most preferably 10⁻⁶ ˜10⁻² mole,per mole of aromatic dihydroxy compounds.

These is no restriction on conditions such as temperature and pressureduring the melt polymerization reaction. The usual conditions for knownprocesses can be used. The first-stage reaction is preferably carriedout at 80°˜250° C., more preferably 100°˜230° C., most preferably120°˜190° C., preferably for a period of 0˜5 hours, more preferably 0˜4hours, most preferably 0.25˜3 hours, at ambient pressure. Then thereaction between the aromatic dihydroxy compounds and the carbonatediesters proceeds as the pressure in the reaction system is reduced andthe temperature increased, and finally the reaction between aromaticdihydroxy compounds and carbonate diesters is completed in vacuo,preferably at 0.05˜5 mm Hg and 240°˜320° C.

The reaction between the types of aromatic dihydroxy compounds andcarbonate diesters described above may be carried out continuously orbatchwise. The apparatus used for this reaction may be a tank, a tubularreactor, or a reaction column.

Polycarbonates of this sort should preferably have an intrinsicviscosity, measured at 20° C. in methylene chloride, of 0.30˜0.65 dL/g,most preferably 0.32˜0.62 dL/g, especially if the resin composition isto be used for optical applications. If the intrinsic viscosity is toohigh, the melt flow of the material will be lowered, making it necessaryto mold it at temperatures in excess of 400° C. At such temperatures itwould be impossible to avoid decomposition of the resin, which couldcause silver streaks or otherwise impair the transparency of the moldedproducts. If the intrinsic viscosity is too low, there may be impairmentof properties such as strength and heat resistance, and molding problemssuch as a tendency to crystallize easily.

The second essential condition in the present invention is that theresin composition contain 0.001˜5 wt. parts esters of aliphaticcarboxylic acids and alcohols per 100 wt. parts polycarbonates.

There is no particular restriction on the esters of aliphatic carboxylicacids and alcohols; various known esters of this type can be used.Examples include, but are not limited to, esters of saturated orunsaturated aliphatic carboxylic acids, dicarboxylic acids, ortricarboxylic acids with saturated or unsaturated monohydric alcoholssuch as ethanol or trifluoroethanol, saturated or unsaturated dihydricalcohols such as ethylene glycol or diethylene glycol, saturated orunsaturated trihydric alcohols such as glycerol, saturated orunsaturated tetrhydric alcohols such as pentaerythritol, and saturatedor unsaturated polyhydric alcohols having functionality of 5 or more.Note that here "aliphatic carboxylic acids" includes alicycliccarboxylic acids. It is preferably to use esters of aliphatic carboxylicacids represented by the formulas ps

    C.sub.n H.sub.2n+a --COOH

or

    HOOC--C.sub.n H.sub.2n --COOH

(where n is an integer 5˜34) with alcohols represented by any of thefollowing formulas ##STR6## (wherein n° is an integer 1˜20; R¹ and R²are each independently an alkyl or substituted alkyl group having 1˜10carbon atoms; or else R¹ and R² are linked to form a 5- or 6-memberring; R³ and R⁵ are each independently an alkyl or substituted alkylgroup having 1˜4 carbon atoms; R⁴ is an alkylene group having 1˜4 carbonatoms or else --(CH₂)_(n') --O--(CH₂)_(n') --, n' being an integer 1˜4).Examples of such carboxylic acids include stearic acid, valeric acid,capric acid, caprylic acid, lauric acid, arachic acid, behenic acid,lignoceric acid, cerotic acid, melissic acid, tetratriacontanoic acid,glutaric acid, adipic acid, azelaic acid, etc. Examples of alcoholsrepresented by the above formulas include 2,2-dihydroperfluoropropanol,neopentyl glycol, pentaerythritol, ditrimethylolpropane,dipentaerythritol, etc. It is more preferable to use esters of aliphaticcarboxylic acids, with dihydric or polyhydric alcohols. A particularlypreferred ester is pentaerythritol tetra-stearate. Of course, one canalso use esters having unsaturated bonds, such as pentaerythritoltriacrylate or trimethylolpropane trimethacylate, and esters ofaliphatic carboxylic acids with alcohols having aryl or othersubstituent groups. It is also possible to use a plurality of differentesters in accordance with the present invention. The amount of estersused should be 0.001˜5 wt. parts preferably 0.01˜1 wt. part, per 100 wt.parts of polycarbonates. If the amount of esters used is less than 0.001wt. part, there will be little improvement in mold releasecharacteristics. On the other hand, if more than 5 wt. parts is used,the mold release characteristics will be improved but the thermalstability and mechanical properties of the composition, in particularits impact strength, will be impaired.

Resin compositions in accordance with the present invention alsopreferably contain 0.1˜10 ppm, most preferably 0.5˜5 ppm, of acidicsulfur-containing compounds having a pK_(a) of 3 or below, orderivatives of such compounds. They make the polycarbonate resincompositions more heat resistant, in particular by inhibiting molecularweight reduction during molding. Any sulfur-containing compound having apK_(a) of 3 or below, or derivative thereof, may be used. Preferredcompounds include those represented by the following formula ##STR7##(where R^(h) is an alkyl group having 1˜50 carbons, in which halogenatoms maybe substituted for hydrogen atoms; R¹ is a hydrogen atom or analkyl group having 1˜50 carbons, in which halogen atoms may besubstituted for halogen atoms; and m' is an integer 0˜3). Specificexamples of such compounds include, but are not limited to, sulfonicacids such as benzenesulfonic acid and p-toluenesulfonic acid; sulfonicacid esters such as methyl benzenesulfonate, ethyl benzenesulfonate,butyl benzenesulfonate, octyl benzenesulfonate, phenyl benzenesulfonate,methyl p-toluenesulfonate, ethyl p-toluenesulfonate, butylp-toluenesulfonate, octyl p-toluenesulfonate, and phenylp-toluenesulfonate; and compounds such as trifluoromethanesulfonic acid,naphthalenesulfonic acid, sulfonated polystyrene, methylacrylate-sulfonated styrene copolymer, etc. It is also possible to usetwo or more of these compound together. Butyl p-toluenesulfonate isparticularly preferred.

Polycarbonate resin compositions in accordance with the presentinvention may also contain added boron compounds. The boron compoundsmay be boric acid or borate esters such as those listed previously ascatalyst components. Adding such boron compounds can preventdiscoloration of the polycarbonate resin composition during molding. Theamount of boron compounds added is preferably about 0.00001˜0.2 wt.part, most preferably about 0.00005˜0.02 wt. part, per 100 wt. parts ofpolycarbonate. If boron compounds are added as catalyst componentsduring polymerization of the polycarbonate, there is no need to add moreafter polymerization.

However, if the amount of such boron compounds or acidic sulfurcompounds or derivatives used is excessive, the water resistance of thepolycarbonate resin composition may be lowered.

Polycarbonate resin compositions in accordance with the presentinvention may also contain phosphorus compounds or carboxylate estersadded as processing stabilizers (antioxidants). Among the phosphoruscompounds which may be used are phosphate esters and phosphite esters.Examples of phosphate esters include trialkyl phosphates such astrimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctylphosphate, tridecyl phosphate, trioctadecyl phosphate, distearylpentaerythrityl diphosphate, tris(2-chloroethyl) phosphate, andtris(2,3-dichloropropyl) phosphate; tricycloalkyl phosphates such astricyclohexyl phosphate; and triaryl phosphates such as triphenylphosphate, tricresyl phosphate, tris(nonylphenyl) phosphate, and2-ethylphenyl diphenyl phosphate. Examples of phosphite esters includetrialkyl phosphites such as trimethyl phosphite, triethyl phosphite,tributyl phosphite, trioctyl phosphite, tris(2-ethylhexyl) phosphite,trinonyl phosphite, tridecyl phosphite, trioctadecyl phosphite,tristearyl phosphite, tris(2-chloroethyl) phosphite, andtris(2,3-dichloropropyl) phosphite; tricycloalkyl phosphites such astricyclohexyl phosphite; triaryl phosphites such as triphenyl phosphite,tricresyl phosphite, tris(ethylphenyl) phosphite,tris(2,4-di-tert-butylphenyl) phosphite, tris(nonylphenyl) phosphite,and tris(hydroxylphenyl) phosphite; aryl alkyl phosphites such as phenyldidecyl phosphite, diphenyl decyl phosphite, iphenyl isooctyl phosphite,phenyl isooctyl phosphite, and 2-ethylhexyl diphenyl phosphite; as wellas distearyl pentaerythrityl diphosphite,bis(2,4-di-tert-butylphenyl)pentaerythrityl diphosphite, and phosphiteesters represented by the general formula

    P(OR.sup.j).sub.3

(where each R^(j) is independently an aliphatic hydrocarbyl group,alicyclic hydrocarbyl group, or aromatic hydrocarbyl group). One canalso use hypophosphorous acid, pyrophosphoric acid, polyphosphoric acid,etc. Of these various compounds, phosphite esters are preferred,especially tris(2,4-di-tert-butylphenyl) phosphite. Examples ofcarboxylate esters, in addition to the compounds previously listed,include but are not limited to n-octadecyl3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate, various alicyclicdiepoxy carboxylates, etc. Two or more stabilizers may be used together.These compounds are preferably used in amounts not exceeding 0.1 wt.part per 100 wt. parts of polycarbonate.

Polycarbonate resin compositions in accordance with the presentinvention also preferably contain epoxy compounds, so that excess boroncompounds or acidic sulfur compounds present in the resin compositionwill react with the epoxy compounds and be neutralized, making itpossible to form moldings having excellent color tone, heat resistance,water resistance, etc. The epoxy compounds used may be any compoundshaving one or more epoxy groups per molecule. Examples include, but arenot limited to, epoxidized soybean oil, epoxidized linseed oil, phenylglycidyl ether, allyl glycidyl ether, tert-butylphenyl glycidyl ether,3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,3,4-epoxy-6-methylcyclohexylmethyl3,4-epoxy-6-methylcyclohexanecarboxylate, 2,3-epoxycyclohexylmethyl3,4-epoxycyclohexanecarboxylate, 4-(3,4-epoxy-5-methylcyclohexyl)butyl3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexanecarboxylate, oxide,cyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,3,4-epoxy-6-methylcyclohexylmethyl 6-methylcyclohexanecarboxylate,bisphenol A diglycidyl ether, tetrabromobisphenol A glycidyl ether, thediglycidyl ester of phthalic acid, the diglycidyl ester ofhexahydrophthalic acid, bis(epoxydicyclopentadienyl) ether,bis-epoxyethylene glycol [sic], bis(epoxycyclohexyl) adipate, butadienediepoxide, tetraphenylethylene epoxide, octyl epoxy talate [sic],epoxidized polybutadiene, 3,4-dimethyl-1,2-epoxycyclohexane,3,5-dimethyl-1,2-epoxycyclohexane,3-methyl-5-tert-butyl-1,2-epoxycyclohexane, octadecyl2,2-dimethyl-3,4-epoxycyclohexanecarboxylate, n-butyl2,2-dimethyl-3,4-epoxycyclohexanecarboxylate, cyclohexyl2-methyl-3,4-epoxycyclohexanecarboxylate, n-butyl2-isopropyl-3,4-epoxy-5-methylcyclohexanecarboxylate, octadecyl3,4-epoxycyclohexanecarboxylate, 2-ethylhexyl3',4'-epoxycyclohexanecarboxylate, 4,6-dimethyl 2,3-epoxycyclohexyl3',4'-epoxycyclohexanecarboxylate, 4,5-epoxytetrahydrophthalicanhydride, 3-tert-butyl-4,5-epoxytetrahydrophthalic anhydride, diethyl4,5-epoxy-cis-1,2-cyclopentanedicarboxylate, di-n-butyl3-tert-butyl-4,5-epoxy-cis-1,2-cyclopentanedicarboxylate, etc. Theseepoxy compounds may be used singly, or in combinations of two or more.There is no particular limitation on the amount of epoxy compounds used,but is is usually preferable to add 0.001˜0.1 wt. part, most preferably0.001˜0.08 wt. part, per 100 wt. parts of polycarbonates.

Polycarbonate resin compositions in accordance with the presentinvention may also contain one or more common additives such as heatstabilizers, weather stabilizers, antistatic agents, slip agents,antiblocking agents, antifogging agent, lubricants, dyes, pigments,natural oils, synthetic oils, waxes, organic fillers, inorganic fillers,etc., in amounts which do not interfere with the object of the presentinvention.

There is no particular restriction on the method used to combine thesecomponents to form resin compositions in accordance with the presentinvention. The components may be mixed in any order. For example, theesters and any optional components may be added to the moltenpolycarbonate and kneaded, or the esters and any optional components maybe added to a solution of the polycarbonate and later kneaded. Morespecifically, the molten polycarbonate reaction product obtained oncompletion of polymerization may be mixed in the reaction vessel orextruder with the esters and any optional components, either one afteranother or all at once. Or the polycarbonate may be pelletized first,and the pellets then fed to a single-screw or twin-screw extruder alongwith the esters and any optional components, and melt kneaded. It isalso possible to dissolve the polycarbonate in a suitable solvent (e.g.,methylene chloride, chloroform, toluene, tetrahydrofuran, etc.), thenadd the esters and any optional components to the solution, either oneafter another or all at once, while stirring.

Polycarbonate resin compositions in accordance with the presentinvention are preferably subjected to a vacuum treatment. There is noparticular restriction on the process or equipment used for vacuumtreatment. For example, one could use a reactor having a vacuum device,or a vacuum-vented extruder. The reactor having a vacuum pumping devicemay be either a vertical tank reactor or a horizontal tank reactor,although horizontal tank reactors are preferred. The vacuum-ventedextruder may be either a single-screw or a twin-screw extruder, whichcarries out the vacuum treatment while pelletizing the polymer. If thevacuum treatment is performed in an evacuated reactor vessel, thepressure is preferably lowered to 0.05˜750 mm Hg, most preferably 0.05˜5mm Hg. If the vacuum treatment is performed in an extruder, the pressureis preferably lowered to 1˜750 mm Hg, most preferably 5˜700 mm Hg. Thiskind of vacuum treatment is preferably performed at 240°˜350° C., for aperiod of 5 minutes to 3 hours in a reactor, or 10 seconds to 15 minutesin an extruder. Performing such a vacuum treatment makes it possible toobtain polycarbonate compositions containing less residual monomers oroligomers. For example, in the case of melt polymerization usingdiphenyl carbonate as the carbonate diester, vacuum treatment candecrease the amount of residual diphenyl carbonate in the polycarbonate.The polycarbonate should preferably contain no more than 0.1 wt. part,most preferably no more than 0.01 wt. part, of residual diphenylcarbonate.

Resin compositions thus obtained, in accordance with the presentinvention, show good mold release and thermal stability, with verylittle discoloration or mold fouling when they are molded.

The present invention will not be described in greater detail by meansof some examples, although it is by no means limited to these examples.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference Example 1

Synthesis of Polycarbonate (PCl) by Melt Process

A 250-liter stirred tank reactor was filled with 0.44 kilomole ofbisphenol A (from Nihon GE Plastics) and 0.44 kilomole of diphenolcarbonate (from Eni Co.), then purged with nitrogen, and the contentswere melted at 140° C.

The temperature was raised to 180° C., 0.011 mole of triphenyl boratewas added, and the mixture was stirred for 30 minutes.

Then 0.00044 mole of sodium hydroxide and 0.11 mole oftetramethylammonium hydroxide were added as catalysts, and stirring wascontinued for 30 minutes, after which the temperature was raised to 210°C. as the pressure was gradually lowered to 200 mm Hg. After 30 minutes,the temperature was increased to 240° C. and the pressure graduallylowered to 15 mm Hg. The temperature and pressure were then keptconstant, and the amount of phenol distilled off was measured. Whenphenol stopped distilling off, the reactor was pressurized with nitrogento atmospheric pressure. The time required for the reaction was 1 hour.

The intrinsic viscosity (η) of the reaction product was 0.15 dL/g.

The reaction product was then fed by a gear pump to a centrifugalthin-film evaporator for further reaction. The evaporator temperatureand pressure were controlled at 270° C. and 2 mm Hg. A gear pump wasused to feed the product from the bottom of the evaporator at a rate of40 kg/hr to a horizontal twin-impeller stirred tank (L/D=3), impellerblade diameter 220 mm, capacity 80 liters), where polymerization wascontinued at 290° C. and 0.2 mm Hg, with a residence time of 30 minutes.

The molten polymer was then fed by a gear pump to a twin-screw extruder(L/D=17.5, barrel temperature 285° C.), to which 2 ppm of butylp-toluenesulfonate was added and kneaded into the polymer. The resultingpolymer was extruded through a die to form a strand, and cut intopellets.

The intrinsic viscosity (IV) of the polymer thus obtained was 0.49 dL/g.

Reference Example 2

Synthesis of Lower-Viscosity Polycarbonate (PC3) by Melt Process

A reaction product obtained as in the first part of Reference Example 1,having intrinsic viscosity (η) 0.15 dL/g, was fed by a gear pump to acentrifugal thin-film evaporator for further reaction. The evaporatortemperature and pressure were controlled at 270° C. and 2 mm Hg. A gearpump was used to feed the product from the bottom of the evaporator at arate of 40 kg/hr to a horizontal stirred tank with twin impellers(L/D=3, impeller blade diameter 220 mm, capacity 80 liters) wherepolymerization was continued at 280° C. and 0.2 mm Hg, with a residencetime of 30 minutes.

The molten polymer was then fed by a gear pump to a twin-screw extruder(L/D=17.5, barrel temperature 285° C.), to which 2 ppm of butylp-toluenesulfonate was added and kneaded into the polymer, which wasextruded through a die to form a strand, and cut into pellets.

The intrinsic viscosity (IV) of the polymer thus obtained was 0.345dL/g.

Examples 1˜2, Comparisons 1˜4

The following components were combined in the proportions shown in Table1, mixed in a single-screw extruder (L/D=17.5, temperature 280° C.), andpelletized.

PC1: polycarbonate obtained in Reference Example 1

PC2: polycarbonate made from bisphenol A by phosgene process (intrinsicviscosity 0.50 dL/g)

PETS: pentaerythritol tetrastearate

TSF437®: silicon oil, from Toshiba Silicone

Stabilizers:

Stb1: tris(2,4-di-tert-butylphenyl) phosphite [MK 2112E®, from AdekaArgus]

Stb2: n-octadecyl 3-(4'-hydroxy-3', -5'-di-tert-butylphenyl)propionate

Stb3: alicyclic diepoxy carboxylate [Celloxide 2021P®, from Daicel]

The resulting pellets were fed to a single-screw extruder (L/D=28,temperature 280° C.), then to a 150-t injection-molding machine(cylinder temperature 280° C., mold temperature 80° C.) to form moldings(150 mm high, 80 mm wide, 70 mm thick).

The moldings thus obtained were evaluated as follows.

Ejector Pin Force (kg,) (mean, n=10): The force applied by the ejectorpin, measured during ejection of the moldings

Deformation by Ejector Pin: Each molding was examined visually fordeformation at the point where the ejector pin struck it.

Mold Fouling (after 10,000 shots): The polished surfaces of the moldwere examined visually for fouling after continuous molding of 3-mmplates (cylinder temperature 290° C., injection pressure 1000 kg/cm²,cycle time 45 sec, mold temperature 90° C.) for a total of 10,000 shots

Initial YI (Yellowness Index): The X, Y, and Z values of the 3-mm plates(molded at cylinder temperature 290° C., injection pressure 1000 kg/cm²,cycle time 45 sec, mold temperature 90° C.) were measured by thetransmission method using an ND-1001 DP Color and Color Difference Meter(from Nippon Denshoku Kogyo), and the yellowness index was calculatedusing the formula YI=100X (1.277X-1.606Z)/Y

YI After 15 Minutes at 320° C. ("320-15 YI" in Table 1): Injectionmoldings were prepared as above, except that the cylinder temperaturewas 320° C. and the composition was held in the cylinder for 15 minutesbefore injection, then the YI of the moldings was determined as above.

Initial MI (melt index): The melt index of the pelletized compositionwas measured by the JIS K-7210 standard method, at 300° C. with a loadof 1.2 kg.

MI After 15 Minutes at 320° C. ("320-15 MI" in Table 1): Measured as forthe initial MI, using plates molded after holding up the resin for 15minutes at 320° C. as described above

The results are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Experiment*                                                                              Ex. 1  Ex. 2  Co. 1 Co. 2 Co. 3 Co. 4                              ______________________________________                                        Composition                                                                   PC1        100    100    --    --    100   100                                PC2        --     --     100   100   --    --                                 PETS       0.3    0.6    0.3   0.6   --    --                                 TSF437     --     --     --    --    --    0.3                                Stb1       0.03   0.03   0.03  0.03  0.03  0.03                               Stb2       0.03   0.03   0.03  0.03  0.03  0.03                               Stb3       0.03   0.03   0.03  0.03  0.03  0.03                               Characteristic                                                                Ejector Pin Force                                                                        740    635    750   630   980   878                                Deformation by                                                                           none   none   none  none  much  much                               Ejector Pin                                                                   Mold Fouling                                                                             none   none   some  some  none  some                               After 10,000 Shots                                                            Initial YI 1.8    1.8    1.8   1.9   1.7   1.8                                320-15 YI  1.8    1.9    2.3   2.5   1.7   1.8                                Initial MI 10.6   11.0   10.3  11.0  10.4  10.7                               320-15 MI  11.0   11.5   13.9  14.3  11.0  11.6                               ______________________________________                                         *Ex. → Example, Co. →  Comparison                          

Examples 3˜4 Comparisons 5˜7

The following components were combined in the proportions shown in Table2, and used to mold compact disks (CDs) 120 mm in diameter using anickel stamper, with a cylinder temperature of 350° C., a cycle time of7 seconds, and a mold temperature of 80° C., in a continuous operationfor 24 hours.

PC3: polycarbonate obtained in Reference Example 2

PC4: polycarbonate made from bisphenol A by phosgene process (intrinsicviscosity 0.357 dL/g)

PETS

Stb1

Stb3

The resulting CDs were tested for the following characteristics.

Continuous Production Quality: Noted whether problems occurred duringthe continuous production run

Stamper Fouling at 24 hours: After producing CDs continuously asdescribed above for 24 hours, the stamper was examined visually forfouling

The results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Experiment.sup.1)                                                                            Ex. 3  Ex. 4  Co. 5 Co. 6 Co. 7                                ______________________________________                                        Composition                                                                   PC3            100    100    --    --    100                                  PC4            --     --     100   100   --                                   PETS           0.1    0.3    0.1   0.3   --                                   Stb1           0.01   0.01   0.01  0.01  0.01                                 Stb3           0.01   0.01   0.01  0.01  0.01                                 Characteristic                                                                Suitability for                                                                              OK     OK     OK    OK    NG.sup.2)                            Continuous Production                                                         Stamper Fouling                                                                              none   none   some  much  --                                   After 24 Hours                                                                ______________________________________                                         .sup.1) Ex. → Example, Co. → Comparison                         .sup.2) Continuous production impossible due to problems caused by poor       mold release (disk sticking in mold, etc.)                               

As can be seen from the examples, resin compositions in accordance withthe present invention show better mold release and thermal stability,and consequently less mold fouling and better continuous productioncharacteristics, than compositions having as their main componentpolycarbonate resins obtained by the phosgene process. Resincompositions in accordance with the present invention also have theadvantage of showing very little discoloration during molding.

What is claimed is:
 1. A polycarbonate resin composition comprising:A)100 parts by weight of a polycarbonate having an intrinsic viscosity, asmeasured at 20 C. in methylene chloride, of from 0.30 to 0.65 dL/g andB) 0.001-5 parts by weight of an ester of an aliphatic carboxylic acidand an alcohol,in which the polycarbonate is a product of meltpolymerization of an aromatic dihydroxy compound with a carbonatediester.
 2. A polycarbonate resin composition of claim 1 wherein theester of an aliphatic carboxylic acid and alcohol is an ester of analiphatic carboxylic acid with a polyhydric alcohol.
 3. A polycarbonateresin composition of claim 2, further comprising 0.1-10 ppm of an acidsulfur-containing compound having a pKa of 3 or less, or a derivativeformed from such a compound.
 4. A polycarbonate resin composition ofclaim 3, wherein the sulfur-containing compound is butylp-toluenesulfonate.
 5. A polycarbonate resin composition of claim 4,wherein the polycarbonate is a product of melt polymerization of anaromatic dihydroxy compound with a carbonate diester in the presence of10⁻⁸ -10⁻³ mole of an alkali metal or alkaline-earth metal compound permold of aromatic dihydroxy compounds.
 6. A melt-polymerizedpolycarbonate resin composition comprising(A) a polycarbonate having anintrinsic viscosity, as measured at 20° C. in methylene chloride of from0.30 to 0.65 dL/g, made by the melt polymer process, and (B) an ester ofan aliphatic carboxylic acid and an alcohol whereby the composition hasgood mold release and thermal stability.
 7. A polycarbonate resincomposition of claim 5 wherein said polycarbonate comprises 100 parts byweight per 0.001-5 parts by weight of said ester.
 8. A process forpreparing a resin composition comprisingmelt-polymerizing from anaromatic dihydroxy compound with a carbonate diester in the presence ofalkali metal or alkaline-earth metal compound a polycarbonate having anintrinsic viscosity, as measured at 20° C. in methylene chloride, offrom 0.30 to 0.65 dL/g, vacuum-treating the polycarbonate at atemperature of from 240° to 350° C. under a vacuum of from 0.05 to 750mm Hg for a period of from 10 seconds to 3 hours and mixing thepolycarbonate with an ester of an aliphatic carboxylic acid and analcohol whereby the composition has good mold release and thermalstability.
 9. A process of claim 8 wherein the polycarbonate is vacuumtreated in an extruder under a vacuum of from 1 to 750 mm Hg for aperiod of from 10 seconds to 15 minutes.
 10. A process of claim 8wherein the polycarbonate is vacuum treated in a reactor vessel under avacuum of from 0.05 to 750 mm Hg for a period of from 5 minutes to 3hours.